Weii, according to the ROCK KB 12000 albums or more is large.
https://kb.roonlabs.com/ROCK:_Storage_Basics
But also remember that it depends on how much DSP you use. If you DSP heavily you need more CPU and RAM speed and size.
Check these out for more information:
https://kb.roonlabs.com/FAQ:_What_are_the_minimum_requirements%3F
Particularly this one.
https://community.roonlabs.com/t/suggested-hardware/90/20?u=brian